Conventional power amplifiers include two types: drop-in power amplifiers and surface mount power amplifiers. FIG. 1 is a schematic structural diagram of a drop-in power amplifier in the prior art, including a substrate 01, a printed circuit board 02 covering an upper surface of the substrate 01, and a power tube 03. A through groove 04 allowing the power tube 03 to pass through is cut into the printed circuit board 02. A mounting groove 05 is cut into the upper surface of the substrate 01 at a location that is corresponding to the through groove 04. One end of the power tube 03 extends through the through groove 04, and is welded onto a bottom face of the mounting groove 05.
To make it convenient for the power tube 03 to pass through the through groove 04 and drop in the mounting groove 05, a size of the mounting groove 05 is 0.25 mm greater than that of the power tube 03 on one side. To improve power amplification consistency, assembly design of a power amplifier requires that the power tube 03 is pushed toward a side of the mounting groove that is close to an output end of the power amplifier, to ensure that there is no gap left between the output end of the power amplifier and a side wall of the mounting groove that is close to the output end of the power amplifier. However, there is consequently no escape channel for gas solder flux during reflow soldering, and a solder void is formed at the bottom of the power tube 03.